Thermal conductivity and thermal expansion behavior of glass fiber-reinforced rigid polyurethane foam

The thermal conductivities and the thermal expansion curves of glass fiber-reinforced rigid polyurethane foams with various fiber lengths, various fiber volume fractions and various matrix densities were determined experimentally. Additionally the thermal expansion coefficients of these materials at room temperature were examined in terms of the interaction between fiber and matrix. The thermal expansion properties were analyzed successfully with the analogous treatment which is applied to the mechanical tensile behavior.     

Carbon fiber having isocyanate group on the surface

Summary Reaction between diisocyanate and the hydroxyl groups on the surface of carbon fiber oxidized by nitric acid was investigated. It was found that polar solvents were favorable for the reaction. Stronger amines and Ba-laurate catalysts gave good results.Further, rigid polyurethane foam reinforced by the carbon fiber thus prepared was found to show improved bending properties.     

Grafting of styrene onto carbon fiber having perester groups

Summary The oxidized carbon fiber having t-butyl perester groups was prepared by the esterification of acid chloride groups on the carbon fiber with t-butyl hydroperoxide. Then, graft polymerization of styrene onto the carbon fiber having t-butyl perester group was carried out. The concentration of monomer affected grafting efficiency. The grafting efficiency increases with the polymerization time and reachs a constant value above 70°C. Addition of Fe ²⁺ and Cu ²⁺ to the polymerization system at a concentration of 0.5–1.0×10 ^-5 mol/l gave the maximum grafting efficiency.     

Development of a color‐tunable polychromatic organic‐light‐emitting‐diode device for roll‐to‐roll manufacturing

A flexible vertically stacked flexible polychromatic color‐tunable OLED has been developed by means of low resistive intermediate electrode technology. The polychromatic OLED has a capability to show 16 million colors with 105% National Television Committee Standard (NTSC) color reproduction. The device can produce arbitrary shape with arbitrary colors, suitable for artistic expressions, just as many as those used in information displays. Independently controlled red, green, and blue light‐emitting layers are stacked vertically. With conventional indium tin oxide technology, because of the temperature restriction, it was quite difficult to achieve low resistance on plastic substrate. The reported numbers were all more than 80 Ω/□. According to the surface mobility control using Fick's law analysis, low sheet resistance 7.34 Ω/□ on plastic film was developed. At first, flexible 7.17 cm² transparent OLED was fabricated for the performance confirmation of transparent electrode. And then polychromatic color‐tunable OLED with the same size were successfully fabricated on plastic. With optical length optimization for each color stack of polychromatic OLED, more than 100% color reproduction in National Television Committee Standard was achieved by stack design. The polychromatic device can be used for colored illumination, as well as for organic‐light‐emitting display pixels for three times emission than conventional pixel design. The device is fabricated on plastic substrate so that the polychromatic organic‐light‐emitting‐diode device is manufacturable with roll‐to‐roll production line.     

Transport Properties of Se/As2Se3 Nanolayer Superlattice Fabricated Using Rotational Evaporation

Since their proposal by Esaki, superlattices have been observed to have fascinating features such as quantum size effects, negative differential resistance, and sequential resonant tunneling. However, the technology threshold for fabricating superlattices is high, requiring methods like molecular beam epitaxy (MBE) and atomic layer deposition (ALD), among others, even for amorphous materials. Thus, the desirable features from superlattices have not been extensively utilized. It is shown that superlattices of Se and As₂Se₃ (superlattice‐Se), fabricated using rotational evaporation, exhibit sequential tunneling, a typical superlattice feature. From current–voltage measurements of the superlattice deposited on n‐type Si, oscillations in the characteristics are observed. Using models of reverse‐biased Schottky barriers, the observations are explained as tunneling in sequence from superlattice minibands. The superlattice‐Se also shows carrier blocking, with a resistivity of the order of 10¹² Ω cm in dark conditions at room temperature, despite the low resistivity (≈10 Ω cm) of the n‐type Si substrate. When the Si is illuminated, the device shows higher detectivity for weaker signals compared to higher illumination. The ease of fabrication, and the blocking and amplifying capabilities make superlattice‐Se an interesting “add‐on” structure to improve conventional photodetector materials such as Si or Ge, which have issues with dark currents at room temperature.     

Digestion and assimilation features of dietary DAG in the rat small intestine

Several recent studies have demonstrated that dietary DAG oil rich in 1,3-species suppresses the postprandial increase of serum TAG level and decreases body fat accumulation, compared with TAG oil. To clarify the mechanisms underlying the beneficial effects of DAG, we investigated the metabolic features of DAG in the small intestine with regard to the digestion pathway in the lumen and the TAG-synthesis pathway in the mucosa. When intraduodenally infused as an emulsion, TAG was digested to 1,2-DAG, 2-MAG, and FFA, whereas 1,3-DAG was digested to 1(3)-MAG and FFA. When assessed by the incorporation of [1-¹⁴C]linoleic acid in lipids, the mucosal TAG-synthesis was significantly reduced by DAG infusion compared with TAG infusion. However, the mucosal 1,3-DAG synthesis was remarkably increased in the DAG-infused rats. The total amount of mucosal 1,3-DAG was also increased (4.5-fold) after DAG infusion compared with that after TAG infusion. Next, we examined the synthesis pathway of 1,3-DAG. In cultures of the everted intestinal sacs, 1,3-DAG production required the presence of 1-MAG, suggesting that the 1,3-DAG synthesis was due to acylation of 1(3)-MAG in the DAG-infused rats. Furthermore, measurements of DAG acyltransferase activity indicated that 1,3-DAG was little utilized in TAG synthesis. These findings suggest that features of 1,3-DAG digestion and assimilation in the intestine may be responsible for the reduction of the postprandial serum TAG level by dietary DAG.     

Risk‐based Replacement Scheme: Rational Replacement under Supply Risk

Though many studies on life extension of power apparatus have been carried out recently, it is inevitable to replace them in the not too distant future. However, if replacements of apparatus occur simultaneously, manufacturers may not able to supply the apparatus within a reasonable cost. This letter proposes a rational replacement scheme to avoid such supply risk. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Numerical investigation of spray combustion in jet mixing type combustor for low NOx emission

The present paper describes a numerical investigation of spray combustion in a jet mixing type combustor. In this combustor, kerosene spray was injected with a pressure atomizer, and high speed combustion air was introduced towards the spray flow through some inlet air nozzles to improve mixing of the spray and the air. In the numerical simulation, the conservative equations of mass, momentum and energy in the turbulent flow field were solved in conjunction with the k–ε two equation turbulence model. The effects of the diameter and the number of air inlet nozzles on the combustion behavior and NO emission were numerically investigated. When the diameter of the inlet air nozzle decreased from 8 to 4 mm, the calculated NO mole fraction in the exhaust gas was drastically decreased by about 80%. An increase in the inlet velocity resulted in improvement of the mixing of the spray and the air, and hence, the high temperature region where thermal NO was formed became narrow. As a result, the exhaust NO mole fraction decreased. Furthermore, a decrease in exhaust NO mole fraction was explained by a decrease in the residence time in the high temperature region above 1800 K.     

Discharge characteristics to insulated material

Lightning strikes not only metallic objects such as transmission towers and lightning rods but also insulated material such as blades of wind turbines. The discharge characteristics of insulated material are, however, not clarified till now. In this paper, discharge characterisitics of insulated material have been investigated experimentally using a 12‐MV impulse generator. The effects of polarities of the applied voltages and surface conditions of the insulation material are also studied and it is found that pollution on the surface decreases the sparkover voltage drastically. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Enhanced Thermal Stability of Red-Emitting Sr2Si5N8:Eu2+ Phosphors from Triggered Applicable Trap Level via Rare Earth Ions Co-Doping

To solve the problem of thermal stability of the red-emitting phosphor Sr₂Si₅N₈:Eu²⁺ with great valuable luminescence performance, trivalent rare earth ions Ln³⁺ (Ln = Dy, Ho, Er, Tm, Nd, and Pr) are co-doped into Sr₂Si₅N₈: Eu²⁺ lattice to form thermally robust phosphors Sr₂Si₅N₈:Eu²⁺,xLn³⁺(Ln_x-258, 0 ≤ x ≤ 0.05). The successful incorporation of rare earth ions in the crystal structure and the regulation of luminescent properties are proven by a variety of material characterization techniques and analysis. Although the co-doping of the selected rare earth ions reduces the luminescence intensity of the phosphor, the Dy_0.01-258 sample still has a high external quantum efficiency (EQE) of 78.6%. More importantly, the co-doping of Dy³⁺ with x = 0.01 significantly improves the luminescent thermal stability of phosphors at high temperature and the luminescence intensity of Dy_0.01-258 samples at 200 °C can be maintained at 94.7% of room temperature. The thermoluminescence spectrum shows that the defects brought about by co-doping of Dy³⁺ with x = 0.01 introduce trap energy levels, which can compensate for the Eu²⁺ luminescence at high temperature. At the same time, the cathodoluminescence mapping and spectra show that the phosphor has a high saturation current under high-energy electron bombardment, which indicates that this nitride phosphor also has the potential to be used in field emission display (FEDs). Based on its extraordinary EQE and thermal stability data, this nitride phosphor is the first-rate among the red phosphors for pc-wLEDs, and has excellent application prospects in FEDs.